The reduction of friction during treatments in the oilfield is an ongoing issue. Various polymeric compositions have been used over the years in attempts to reduce friction in treatment fluids during pressure pumping operations. Guar, polymethylmethacrylate, polyethyleneoxide, polyacrylamide, polyAMPS (poly 2-acrylamido-2-methylpropane sulfonic acid), polymers derived therefrom, and other high molecular weight synthetic polymers, have been used in the oilfield in the past as conventional friction reducers to reduce friction pressures in turbulent flow regimes. Currently, the industry standard for friction reduction in the oilfield is to use polyacrylamide and poly(acrylamide derived) polymers, co-polymers, or mixtures thereof in solution or in emulsified form.
U.S. Pat. No. 3,442,803 to Hoover et al. discloses reducing friction in an aqueous oil well fracturing system by dissolving in the aqueous system a small amount of a copolymer of acrylamide and methylene bis-acrylamide. Such polyacrylamides can be prepared with cationic, anionic or non-ionic end groups, depending on the specific intended application. Polyacrylamide and polyacrylamide derived friction reducers have been used as friction reducers for benchmarking the suspending friction reducing compositions and methods herein.
In tight gas formations, reservoir stimulation techniques often involve water as the main treatment fluid. Since water is a Newtonian fluid, it generates high treatment pressures due to frictional pressure losses at high pump rates. To limit this friction pressure, very low concentrations of generally high molecular weight (several million Dalton) polymer-based conventional friction reducers (CFRs) are added to the fluid with inorganic salts or organic substitutes for clay stabilization. These low-cost fluid systems are commonly referred to in the industry as slick-water fluid systems.
Slick-water fluid systems do not have sufficient viscosity or elasticity to provide good proppant carrying capacity. Therefore, slick-water jobs rely on high pump rates and turbulence to carry low concentrations of proppants into the formation along a hydraulic fracture during fracturing treatments. High rate water pack treatments rely on high pump rates and turbulence to carry low concentrations of gravel into the annulus formed by the well and a screen during gravel packing treatments. One goal of the invention described herein is to achieve effective proppant transport at higher proppant concentrations in the fracture, which will provide better production for the well, or higher gravel concentrations in the annulus, which means more effective gravel packing. A primary benefit of the fluid and method of the invention is that the treatment pump rate can be reduced, and therefore the horsepower required on location can also be reduced. Hence, the invention overall provides both a more efficient and a more cost-effective treatment method.
It has now been discovered that fluids comprising at least one drag reducing surfactant, a polymer and/or a monomer provide improvements over such friction reduction compounds. These fluids exhibit outstanding improved viscous and solid suspending characteristics, over similar fluids reported in the prior art, at low surfactant concentrations.